DESCRIPTION (provided by investigator): The objective of this study is to investigate neuropsychological function in individuals diagnosed with Duchenne muscular dystrophy (DMD) as a model for developmental neuroscience. DMD is a single-gene disorder that interferes with the expression of the protein dystrophin and its isoforms. The consequences of lack of dystrophin in muscle are well known; boys have progressive muscular weakness that results in death generally by their third decade of life. Dystrophin isoforms are also missing from the central nervous system, yet what functional consequences that may have is unclear. Interdisciplinary study of the cognitive profile, the behavioral attributes, and the molecular genetics of DMD will examine genotype/phenotype associations. The study will build on work that ascertained neuropsychological function in a group of 136 boys diagnosed with DMD and was completed during the tenure of an R29 award. Those data confirmed that boys with DMD who are of average intelligence have selective deficits in verbal working memory with intact declarative memory and visuospatial skills, poor social skills and delayed language developmental milestones. Selected subjects from the established cohort will be examined more thoroughly in focused paradigms to tease apart their language and short-term memory skills using a battery of tests designed to examine the hypothetical "phonological loop." Additionally, subjects will be tested on measures of social function and awareness. New subjects will also be enrolled to increase our sample size for genetic analyses. Subjects with more mild manifestations of the disorder (boys with Becker's muscular dystrophy and carrier females) will be tested on neuropsychological measures to determine whether they present with cognitive phenotypes. An ongoing longitudinal study of a sample of 26 boys will be continued with neuropsychological testing every other year. And newly characterized preschool boys with DMD will be followed to track their language and emotional development. [unreadable] [unreadable]